Field of the Invention
This invention relates generally to solar control coatings and, more particularly, to a solar control coating having at least four metal functional layers. One or more of the metal functional layers can be a discontinuous metal layer.
Technical Considerations
Solar control coatings block or filter selected ranges of electromagnetic radiation, typically radiation in the infrared region and/or ultraviolet region of the electromagnetic spectrum. These coatings reduce the amount of solar energy entering a building through transparencies, such as windows, which in turn reduces the heat buildup inside the building. The SHGC, i.e., the fraction of the heat from the sun that enters the building through the transparency, is a measure of how well the transparency blocks solar heat.
Conventional solar control coatings typically have from one to three continuous infrared reflective metal layers. While these conventional coatings provide good solar insulation properties, it would be useful to decrease the SHGC of conventional transparencies even further to improve the solar control properties of the transparency. To decrease the SHGC of these conventional solar control coatings, the thicknesses of the continuous infrared reflective metal layers could be increased. However, this would also make the solar control coating more reflective of visible light. The commercial market prefers transparencies with high transmittance but low visible light reflectance (both interior and exterior visible light reflectance). Further, increasing the thicknesses of the continuous infrared reflective metal layers increases the sensitivity of the solar control coating to random or systematic variations in the thicknesses of the films making up the coating. This can alter or adversely impact upon the performance of the coating or the aesthetics of the coating. Additionally, increasing the thicknesses of the continuous infrared reflective metal layers tends to decrease the durability of the coating to chemical and/or mechanical attack. Moreover, the aesthetic/color space that can be reached with conventional solar control coatings is relatively limited.
Therefore, it would be desirable to provide a solar control coating that provides enhanced solar control and/or aesthetic performance compared to conventional solar control coatings. For example, it would be desirable to provide a solar control coating having a lower solar heat gain coefficient (SHGC) compared to conventional solar control coatings. For example, it would be desirable to provide a solar control coating having a higher light to solar gain ratio (LSG) compared to conventional solar control coatings. For example, it would be desirable to provide a solar control coating having more commercially desirable aesthetics and/or a larger available color space compared to conventional solar control coatings. For example, it would be desirable to provide a solar control coating having more chemical and/or mechanical durability compared to conventional solar control coatings.